A new concept of Si microwire anodes for Li ion batteries, which consists of an array of Si microwires embedded at one end in a Cu current collector, has been lately developed . The process for the production of the wires is fully scalable, allowing the production of anodes as large as a silicon wafer, with wires as long as the thickness of the wafer . The method is based in the electrochemical etching of macropores and a chemical over-etching step, what makes it very economical. The capacity of the anodes is very stable over 100 cycles , and breaks all the records when considering the capacity per area (mAh/cm2), with wires of 70 micron in length . This capacity can be even larger when preparing longer wires. Nevertheless, it is not known which may be the limit for scaling up the wires. In the paper for this conference, an electrical and mechanical description of the wires will be given, explaining which are the charging rate limits of the wires. A model based on the series resistance, aging and state of charge will be discussed. Comments of the future development of the wires will be given.  E. Quiroga-Gonzï¿½lez, E. Ossei-Wusu, J. Carstensen, H. Fï¿½ll, J. Electrochem. Soc., 158 (2011) E119.  E. Quiroga-Gonzï¿½lez, E. Ossei-Wusu, J. Carstensen, H. Fï¿½ll, Nanoscale Res. Lett. 9 (2014) 417.  E. Quiroga-Gonzï¿½lez, J. Carstensen, H. Fï¿½ll, Electrochim. Acta, 101 (2013) 93.  E. Quiroga-Gonzï¿½lez, J. Carstensen, H. Fï¿½ll, Energies, 6 (2013) 5145.